19 results on '"Alexandra Viel"'
Search Results
2. Simulation of argon induced coupling coefficients of NH3 doublets and their speed dependence
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Franck Thibault, Alexandra Viel, Christian Boulet, Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences Moléculaires d'Orsay (ISMO), and Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,Radiation ,Line-shape parameters ,Atomic and molecular collisions ,Quantum dynamics ,Molecular physics ,Spectroscopy ,Atomic and Molecular Physics, and Optics - Abstract
International audience; We present a theoretical evaluation of collision induced effects on a few typical doublets in the nu_4 band of ammonia perturbed by argon.Quantum dynamical calculations performed on two NH_3-Ar potential energy surfaces provide pressure broadening and intradoublet generalized cross sections. From these calculations we derive thermally averaged values at various temperatures. The intradoublet coupling terms at room temperature are found to be in good agreement with available data in the literature. In addition, we study the speed dependence of the pressure broadening and intradoublet coupling coefficients. The former show a usual speed dependence, quite important, but the later show a weak speed dependence at least around 296 K and above.
- Published
- 2023
3. Accurate quantum dynamics simulation of the photodetachment spectrum of the nitrate anion (NO
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Alexandra, Viel, David M G, Williams, and Wolfgang, Eisfeld
- Abstract
The photodetachment spectrum of the nitrate anion (NO
- Published
- 2021
4. Accurate quantum dynamics simulation of the photodetachment spectrum of the nitrate anion (NO3−) based on an artificial neural network diabatic potential model
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Alexandra Viel, David M. G. Williams, Wolfgang Eisfeld, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Theoretische Chemie, Universität Bielefeld, Germany, Universität Bielefeld = Bielefeld University, Ei375/6-2, Deutsche Forschungsgemeinschaft, 40442PD, PHC/DAAD Procope, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,010304 chemical physics ,Wave packet ,Quantum dynamics ,Diabatic ,Vibronic couplings ,General Physics and Astronomy ,Electron ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Hot band ,0104 chemical sciences ,Vibronic coupling ,MCTDH ,Excited state ,0103 physical sciences ,Artificial Neuron Networks ANN ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,Ground state ,Spectroscopy - Abstract
International audience; The photodetachment spectrum of the nitrate anion (NO − 3) is simulated from first principles using wavepacket quantum dynamics propagation and a newly developed accurate full-dimensional fully coupled five state diabatic potential model. This model utilizes the recently proposed complete nuclear permutation inversion invariant artificial neural network diabatization technique [D. M. G. Williams and W. Eisfeld, J. Phys. Chem. A 124, 7608 (2020)]. The quantum dynamics simulations are designed such that temperature effects and the impact of near threshold detachment are taken into account. Thus, the two available experiments at high temperature and at cryogenic temperature using the slow electron velocity-map imaging technique can be reproduced in very good agreement. These results clearly show the relevance of hot bands and vibronic coupling between theX 2 A ′ 2 ground state and theB 2 E ′ excited state of the neutral radical. This together with the recent experiment at low temperature gives further support for the proper assignment of the ν 3 fundamental, which has been debated for many years. An assignment of a not yet discussed hot band line is also proposed.
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- 2021
5. Subpercent agreement between ab initio and experimental collision-induced line shapes of carbon monoxide perturbed by argon
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Piotr Masłowski, Grzegorz Kowzan, Alexandra Viel, Hubert Cybulski, Piotr Wcisło, Franck Thibault, Michał Słowiński, Institute of Physics [Toruń], Faculty of Physics, Astronomy and Informatics [Toruń], Nicolaus Copernicus University [Toruń]-Nicolaus Copernicus University [Toruń], Institute of Mathematics and Physics [Bydgoszcz], University of Technology and Life Sciences [ Bydgoszcz], Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), 2017/24/T/ST2/00242, Narodowe Centrum Nauki, Fundacja na rzecz Nauki Polskiej, European Regional Development Fund, Nicolaus Copernicus University [Toruń], and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
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Materials science ,Quantum dynamics ,Ab initio ,chemistry.chemical_element ,01 natural sciences ,Molecular physics ,Spectral line ,010305 fluids & plasmas ,chemistry.chemical_compound ,Ab initio quantum chemistry methods ,0103 physical sciences ,010306 general physics ,Line profiles ,Spectroscopy ,ComputingMilieux_MISCELLANEOUS ,Line (formation) ,Physics ,[PHYS]Physics [physics] ,Argon ,Scattering ,Rotational–vibrational spectroscopy ,Collision ,chemistry ,Atomic and molecular collisions ,Atomic physics ,Carbon monoxide - Abstract
International audience; We present fully ab initio calculations of second-overtone rovibrational line shapes of carbon monoxide perturbed by argon. The quantum mechanical scattering problem between CO and Ar is solved numerically for two different ab initio interaction potentials. We use the generalized Hess method to determine spectroscopic cross sections which describe the effect of collisions on each spectral line. Using these cross sections, we determine the line-shape parameters that we use to generate the Hartmann-Tran and speed-dependent billiard ball profiles. We compare the generated line shapes with high-quality experimental line profiles of five lines measured at five pressures between 0.01 and 1 atm. A subpercent agreement over the entire pressure range is obtained. Calculations for the P(9) line are used to inspect the effects of the two interaction potentials. The discrepancies for both the considered interaction potentials and the experiment are explained within the described theoretical framework. The presented results are the most accurate collisional line-shape calculations for a system with collision dynamics representative of atmospherically relevant species.
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- 2020
6. FULLY AB INITIO SECOND-OVERTONE LINE SHAPES OF CARBON MONOXIDE PERTURBED BY ARGON: A COMPARISON WITH EXPERIMENT
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Alexandra Viel, Piotr Masłowski, Franck Thibault, Michał Słowiński, Piotr Wcisło, Hubert Cybulski, and Grzegorz Kowzan
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chemistry.chemical_compound ,Materials science ,Argon ,chemistry ,Overtone ,Ab initio ,chemistry.chemical_element ,Atomic physics ,Line (formation) ,Carbon monoxide - Published
- 2020
7. Diabatic neural network potentials for accurate vibronic quantum dynamics-The test case of planar NO
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David M G, Williams, Alexandra, Viel, and Wolfgang, Eisfeld
- Abstract
A recently developed scheme to produce high-dimensional coupled diabatic potential energy surfaces (PESs) based on artificial neural networks (ANNs) [D. M. G. Williams and W. Eisfeld, J. Chem. Phys. 149, 204106 (2019)] is tested for its viability for quantum dynamics applications. The method, capable of reproducing high-quality ab initio data with excellent accuracy, utilizes simple coupling matrices to produce a basic low-order diabatic potential matrix as an underlying backbone for the model. This crude model is then refined by making its expansion coefficients geometry-dependent by the output neurons of the ANN. This structure, strongly guided by a straightforward physical picture behind nonadiabatic coupling, combines structural simplicity with high accuracy, reproducing ab initio data without introducing unphysical artifacts to the surface, even for systems with complicated electronic structure. The properties of diabatic potentials obtained by this method are tested thoroughly in the present study. Vibrational/vibronic eigenstates are computed on the X̃ and à states of NO
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- 2019
8. Fully quantum calculations of the line-shape parameters for the Hartmann-Tran profile: a CO-Ar case study
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Piotr Masłowski, Michał Słowiński, Alexandra Viel, Franck Thibault, Grzegorz Kowzan, Piotr Wcisło, Institute of Physics [Toruń], Faculty of Physics, Astronomy and Informatics [Toruń], Nicolaus Copernicus University [Toruń]-Nicolaus Copernicus University [Toruń], Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Nicolaus Copernicus University [Toruń], Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Viel, Alexandra
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Physics ,[PHYS]Physics [physics] ,Radiation ,010504 meteorology & atmospheric sciences ,Dicke effect ,Dephasing ,Quantum dynamics ,Ab initio ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,[PHYS] Physics [physics] ,Quadratic equation ,Quantum electrodynamics ,HITRAN ,Atomic and molecular collisions ,Molecular physics ,Quantum ,Line profiles ,Spectroscopy ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Line (formation) - Abstract
International audience; We present a procedure for generating the parameters of the Hartmann-Tran profile (HTP) from purely first principles calculations. Starting from an absorber-perturber interaction potential, we calculate S-matrices describing the effect of collisions on the absorbing molecule. We then use the generalized Hess method to calculate speed-dependent pressure shift and broadening parameters, and the complex Dicke parameter, ν opt , which accounts for such effects as the Dicke effect and correlations between dephasing and velocity-changing collisions. Based on these ab initio results, we derive the Hartmann-Tran profile parameters and evaluate the validity of the quadratic approximation of speed dependence and the hard-collision model of velocity-changing collisions adopted in the Hartmann-Tran profile. We also discuss the interpretation and speed dependence of ν opt. Finally, we evaluate the approximation scheme for temperature dependence of HTP line-shape parameters adopted in the 2016 edition of the HITRAN database.
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- 2019
9. Quantum dynamics and geometric phase in E⊗e Jahn-Teller systems with general C
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Thomas, Weike, David M G, Williams, Alexandra, Viel, and Wolfgang, Eisfeld
- Abstract
E ⊗ e Jahn-Teller (JT) systems are considered the prototype of symmetry-induced conical intersections and of the corresponding geometric phase effect (GPE). For decades, this has been analyzed for the most common case originating from C
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- 2019
10. Large amplitude motion within acetylene–rare gas complexes hosted in helium droplets
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Alexandra Viel, Jean-Michel Mestdagh, Benoît Soep, E. Mengesha, Pierre Jamet, M. Briant, Marc-André Gaveau, Jean-Michel Launay, Lionel Poisson, Dynamique Réactionnelle (DyR), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Laboratoire Interactions, Dynamiques et Lasers (ex SPAM) (LIDyl), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), GDR 3533 Edifices Moléculaires Isolés et Environnés, Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)
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Materials science ,Quantum dynamics ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Spectral line ,Physics::Plasma Physics ,Bound state ,Astrophysics::Solar and Stellar Astrophysics ,Physical and Theoretical Chemistry ,Spectroscopy ,Helium ,[PHYS]Physics [physics] ,Mesoscopic physics ,Resonance ,021001 nanoscience & nanotechnology ,Potential energy ,0104 chemical sciences ,chemistry ,Helium clusters ,Astrophysics::Earth and Planetary Astrophysics ,Atomic and molecular collisions ,0210 nano-technology - Abstract
International audience; Near-infrared spectroscopy of the C2H2–Ar, Kr complexes was performed in the spectral region overlapping the ν3/ν2 + ν4 + ν5 Fermi-type resonance of C2H2. The experiment was conducted along the HElium NanoDroplet Isolation (HENDI) technique in order to study the coupling dynamics between a floppy molecular system (C2H2–Ar and C2H2–Kr) and a mesoscopic quantum liquid (the droplet). Calculations were performed using a spectral element based close-coupling program and state-of-the-art 2-dimensional potential energy surfaces to determine the bound states of the C2H2–Ar and C2H2–Kr complexes and simulate the observed spectra. This furnished a quantitative basis to unravel how the superfluid and non-superfluid components of the droplet affect the rotation and the deformation dynamics of the hosted complex.
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- 2019
11. Diabatic neural network potentials for accurate vibronic quantum dynamics -The test case of planar NO3
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David M. G. Williams, Alexandra Viel, Wolfgang Eisfeld, Theoretische Chemie, Universität Bielefeld, Germany, Universität Bielefeld = Bielefeld University, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Deutsche Forschungsgemeinschaft, 40442PD, Deutscher Akademischer Austauschdienst, PROCOPE project number 40442PD, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,010304 chemical physics ,Quantum dynamics ,Diabatic ,Ab initio ,Vibronic couplings ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Potential energy ,0104 chemical sciences ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Vibronic coupling ,Matrix (mathematics) ,MCTDH ,0103 physical sciences ,Artificial Neuron Networks ANN ,Statistical physics ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physical and Theoretical Chemistry ,Molecular physics ,Eigenvalues and eigenvectors ,Ansatz - Abstract
International audience; A recently developed scheme to produce high-dimensional coupled diabatic potential energy surfaces (PESs) based on artificial neural networks (ANNs) [D. M. G. Williams and W. Eisfeld, J. Chem. Phys. 149, 204106 (2019)] is tested for its viability for quantum dynamics applications. The method, capable of reproducing high-quality ab initio data with excellent accuracy, utilizes simple coupling matrices to produce a basic low-order diabatic potential matrix as an underlying backbone for the model. This crude model is then refined by making its expansion coefficients geometry-dependent by the output neurons of the ANN. This structure, strongly guided by a straightforward physical picture behind nonadiabatic coupling, combines structural simplicity with high accuracy, reproducing ab initio data without introducing unphysical artifacts to the surface, even for systems with complicated electronic structure. The properties of diabatic potentials obtained by this method are tested thoroughly in the present study. Vibrational/vibronic eigenstates are computed on theX andà states of NO 3 , a notoriously difficult Jahn-Teller system featuring strong nonadiabatic couplings and complex spectra. The method is investigated in terms of how consistently it produces dynamics results for PESs of similar (fitting) quality and how the results depend on the ANN size and ANN topography. A central aspect of this work is to understand the convergence properties of the new method in order to evaluate its predictive power. A previously developed, high-quality model utilizing a purely (high-order) polynomial ansatz is used as a reference to showcase improvements of the overall quality which can be obtained by the new method.
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- 2019
12. Quantum dynamics and geometric phase in E ⊗ e Jahn-Teller systems with general Cnv symmetry
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David M. G. Williams, Alexandra Viel, Wolfgang Eisfeld, Thomas Weike, Theoretische Chemie, Universität Bielefeld, Germany, Universität Bielefeld = Bielefeld University, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), PHC PROCOPE 40442PD, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,010304 chemical physics ,Jahn–Teller effect ,Quantum dynamics ,Diabatic ,Vibronic couplings ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Vibronic coupling ,symbols.namesake ,Geometric phase ,Quantum mechanics ,0103 physical sciences ,Potential energy surface ,symbols ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physical and Theoretical Chemistry ,Adiabatic process ,Hamiltonian (quantum mechanics) ,Molecular physics - Abstract
International audience; E ⊗ e Jahn-Teller (JT) systems are considered the prototype of symmetry-induced conical intersections and of the corresponding geometric phase effect (GPE). For decades, this has been analyzed for the most common case originating from C 3v symmetry and these results usually were generalized. In the present work, a thorough analysis of the JT effect, vibronic coupling Hamiltonians, GPE, and the effect on spectro-scopic properties is carried out for general Cnv symmetric systems (and explicitly for n = 3-8). It turns out that the C 3v case is much less general than often assumed. The GPE due to the vibronic Hamiltonian depends on the leading coupling term of a diabatic representation of the problem, which is a result of the explicit n, α, and β values of a Cnv Eα ⊗ e β system. Furthermore, the general existence of n/m (m ∈ N depending on n, α, and β) equivalent minima on the lower adiabatic sheet of the potential energy surface (PES) leads to tunneling multiplets of n/m states (state components). These sets can be understood as local vibrations of the atoms around their equilibrium positions within each of the local PES wells symmetrized over all equivalent wells. The local vibrations can be classified as tangential or radial vibrations, and the quanta in the tangential mode together with the GPE determine the level ordering within each of the vibronic multiplets. Our theoretical predictions derived analytically are tested and supported by numerical model simulations for all possible Eα ⊗ e β cases for Cnv symmetric systems with n = 3-8. The present interpretation allows for a full understanding of the complex JT spectra of real systems, at least for low excitation energies. This also opens a spectroscopic way to show the existence or absence of GPEs. Published under license by AIP Publishing. https://doi.
- Published
- 2019
13. NO3 full-dimensional potential energy surfaces and ground state vibrational levels revisited
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Wolfgang Eisfeld, Alexandra Viel, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Theoretische Chemie, Universität Bielefeld, Germany, Universität Bielefeld = Bielefeld University, Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes ( IPR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), and Bielefeld University
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[PHYS]Physics [physics] ,Range (particle radiation) ,[ PHYS ] Physics [physics] ,010304 chemical physics ,Chemistry ,Quantum dynamics ,Diabatic ,Vibronic couplings ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Potential energy ,0104 chemical sciences ,Dipole ,MCTDH ,Ab initio quantum chemistry methods ,0103 physical sciences ,Potential energy surface ,Physical and Theoretical Chemistry ,Atomic physics ,Ground state ,Molecular physics ,ComputingMilieux_MISCELLANEOUS - Abstract
A new full-dimensional (6D) diabatic potential energy surface (PES) model is presented representing the five lowest PESs corresponding to the X 2 A 2 ′ , A 2 E ″ , and B 2 E ′ electronic states of the nitrate radical (NO3). It is based on high-level ab initio calculations of roughly 90000 energy data over a wide range of nuclear configurations and represents the energies with a root mean-squares (rms) error of about 100 cm−1. An accurate dipole surface was developed for the X state as well. The new PES model is used to re-investigate the infra-red (IR) spectrum corresponding to the electronic ground state by full dimensional quantum dynamics simulations. Vibrational eigenstates, IR transition probabilities, and isotopic shifts are computed and analyzed. Levels up to 2000 cm−1 are obtained and show good to excellent agreement with known experimental values. Some larger deviations are observed and discussed as well. The new results are in agreement with previous theoretical studies that the disputed ν 3 fundamental corresponds to a frequency of roughly 1022 cm−1 and that the prominent experimental feature observed at 1492 cm−1 is due to the 3 1 4 1 ( e ′ ) combination mode. Observed discrepancies in the IR intensities may be explained by coupling to the B state which is also analysed by diabatic decomposition of the eigenstates.
- Published
- 2018
14. Application of the spectral element method to the solution of the multichannel Schroedinger equation
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Alexandra Viel, Jean-Michel Launay, Andrea Simoni, Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), ANR-12-BS04-0020-01, Agence Nationale de la Recherche (ANR), ANR-12-BS04-0020,COLORI,Collisions moléculaires ultrafroides en présence d'interactions à longue portée dans des géométries confinées(2012), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,Discretization ,Scattering ,Spectral element methods ,Mathematical analysis ,Spectral element method ,General Physics and Astronomy ,01 natural sciences ,010305 fluids & plasmas ,Schrödinger equation ,symbols.namesake ,Matrix (mathematics) ,Cold and ultra-cold collisions ,0103 physical sciences ,Bound state ,symbols ,Boundary value problem ,Atomic and molecular collisions ,Physical and Theoretical Chemistry ,Quantum dynamics ,010306 general physics ,Molecular physics ,Physics - Computational Physics ,Sparse matrix - Abstract
We apply the spectral element method to the determination of scattering and bound states of the multichannel Schr\"odinger equation. In our approach the reaction coordinate is discretized on a grid of points whereas the internal coordinates are described by either purely diabatic or locally diabatic (diabatic-by-sector) bases. Bound levels and scattering matrix elements are determined with spectral accuracy using relatively small numbers of points. The scattering problem is cast as a linear system solved using state-of-the-art sparse matrix non iterative packages. Boundary conditions can be imposed so to compute a single column of the matrix solution. A comparison with log-derivative propagators customarily used in molecular physics is performed. The same discretization scheme can also be applied to bound levels that are computed using direct scalable sparse-matrix solvers., Comment: 24 pages, 5 figures
- Published
- 2017
15. Vibronic eigenstates and the geometric phase effect in the
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Wolfgang, Eisfeld and Alexandra, Viel
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The
- Published
- 2017
16. Vibronic eigenstates and the geometric phase effect in the 2 E″ state of NO 3
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Wolfgang Eisfeld, Alexandra Viel, Faculty of Chemistry, Universität Bielefeld = Bielefeld University, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), INTEGER project included in the No. EU 7ePC/2007-2013 program with the Convention No. 266638, European Project: 266638,EC:FP7:SiS,FP7-SCIENCE-IN-SOCIETY-2010-1,INTEGER(2011), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
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Quantum dynamics ,Jahn–Teller effect ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,MCTDH ,Quantum mechanics ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Vibronic spectroscopy ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Quantum tunnelling ,[PHYS]Physics [physics] ,010304 chemical physics ,Chemistry ,Vibronic couplings ,Hartree ,0104 chemical sciences ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Vibronic coupling ,Geometric phase ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Atomic physics ,Ground state ,Molecular physics - Abstract
The E-2 '' state of NO3, a prototype for the Jahn-Teller effect, has been an enigma and a challenge for a long time for both experiment and theory. We present a detailed theoretical study of the vibronic quantum dynamics in this electronic state, uncovering the effects of tunnelling, geometric phase, and symmetry. To this end, 45 vibronic levels of NO3 in the E-2 '' state are determined accurately and analyzed thoroughly. The computation is based on a high quality diabatic potential representation of the two-sheeted surface of the E-2 '' state developed by us [W. Eisfeld et al., J. Chem. Phys. 140, 224109 (2014)] and on the multi-configuration time dependent Hartree approach. The vibrational eigenstates of the NO3- anion are determined and analyzed as well to gain a deeper understanding of the symmetry properties of such D-3h symmetric systems. To this end, 61 eigenstates of the NO3- anion ground state are computed using the single sheeted potential surface of the (1)A(1) state published in the same reference quoted above. The assignments of both the vibrational and vibronic levels are discussed. A simple model is proposed to rationalize the computed NO3 spectrum strongly influenced by the Jahn-Teller couplings, the associated geometric phase effect, and the tunnelling. Comparison with the available spectroscopic data is also presented. Published by AIP Publishing.
- Published
- 2017
17. LiHe spectra from brown dwarfs to helium clusters
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Grégoire Guillon, John F. Kielkopf, Frank Stienkemeier, Nicole F. Allard, Akira Nakayama, Alexandra Viel, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Division of Chemistry, Graduate School of Science, Hokkaido University [Sapporo, Japan], Physikalisches Institut [Freiburg], Albert-Ludwigs-Universität Freiburg, Department of Physics and Astronomy [Louisville], University of Louisville, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
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Atmospheric Science ,Line: profiles ,Brown dwarf ,Aerospace Engineering ,chemistry.chemical_element ,Astrophysics ,Stellar classification ,Resonance (particle physics) ,Spectral line ,Stars: atmospheres-brown dwarfs ,chemistry.chemical_compound ,Astrophysics::Solar and Stellar Astrophysics ,LiHe ,Spectroscopy ,Astrophysics::Galaxy Astrophysics ,Helium ,Line (formation) ,Physics ,Solar mass ,Astronomy and Astrophysics ,[PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph] ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Geophysics ,chemistry ,Helium clusters ,Space and Planetary Science ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Atomic physics ,Atomic and molecular clusters ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
International audience; The detection of Li I lines is the most decisive spectral indicator of substellarity for young brown dwarfs with masses below about 0.06 solar mass. Due to the weakness of the Li resonance lines, it is important to be able to model precisely both their core widths and their wing profiles. This allows an adequate prediction of the mass at which Li lines reappear in the spectra of brown dwarfs for a given age, or reversely an accurate determination of the age of a cluster. We report improved line profiles and the dependence of line width on temperature suitable for modeling substellar atmospheres that were determined from new LiHe molecular potential energies. Over a limited range of density and temperature, comparison with laboratory measurements was used to validate the potential energies which support the spectral line profile theory.
- Published
- 2014
18. Feshbach resonances and weakly bound molecular states of boson-boson and boson-fermion NaK pairs
- Author
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Andrea Simoni, Alexandra Viel, Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), ANR-12-BS04-0020, Agence Nationale de la Recherche, ANR-12-BS04-0020,COLORI,Collisions moléculaires ultrafroides en présence d'interactions à longue portée dans des géométries confinées(2012), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)
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Quantum dynamics ,FOS: Physical sciences ,01 natural sciences ,010305 fluids & plasmas ,Cold and ultra-cold collisions ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,0103 physical sciences ,Bound state ,Atomic and molecular physics ,010306 general physics ,Spectroscopy ,Feshbach resonance ,Boson ,Physics ,[PHYS]Physics [physics] ,Condensed Matter::Quantum Gases ,Scattering ,Chemical polarity ,Fermion ,3. Good health ,Quantum Gases (cond-mat.quant-gas) ,Atomic and molecular collisions ,Atomic physics ,Condensed Matter - Quantum Gases ,Molecular physics - Abstract
We study theoretically magnetically induced Feshbach resonances and near-threshold bound states in isotopic NaK pairs. Our calculations accurately reproduce Feshbach spectroscopy data on Na$^{40}$K and explain the origin of the observed multiplets in the p-wave [Phys. Rev. A 85, 051602(R) (2012)]. We apply the model to predict scattering and bound state threshold properties of the boson-boson Na$^{39}$K and Na$^{41}$K systems. We find that the Na$^{39}$K isotopic pair presents broad magnetic Feshbach resonances and favorable ground-state features for producing non-reactive polar molecules by two-photon association. Broad s-wave resonances are also predicted for Na$^{41}$K collisions., Comment: 39 pages, 15 figures. Phys. Rev. A in press
- Published
- 2016
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19. Temperature dependence of sodium and ionized calcium resonance lines perturbed by helium
- Author
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Grégoire Guillon, Alexandra Viel, Nicolle F Allard, John F. Kielkopf, Derek Homeier, Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Louisville], University of Louisville, CREATE Project '4023 HELIUM', Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
History ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Helium ,01 natural sciences ,Astronomical spectroscopy ,Spectral line ,Education ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010306 general physics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,[PHYS]Physics [physics] ,[PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph] ,Chemistry ,Stellar atmosphere ,White dwarf ,Astronomy ,Planetary system ,[PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,Accretion (astrophysics) ,Computer Science Applications ,Stars ,13. Climate action ,Circumstellar dust ,Atomic and molecular collisions ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Astrophysics::Earth and Planetary Astrophysics ,Molecular physics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
International audience; Traces of heavy metals in cool DZ white dwarf stars may be attributed to the accretion of circumstellar dust thought to originate from tidal disruption of rocky parent bodies. Spectra of such stars therefore provide a unique opportunity to study the composition of extrasolar planetary systems. The determination of metal abundances from stellar spectra depends on stellar atmospheric parameters and an accurate prior knowledge of the collision broadening of the line profiles by the most common constituents of the stellar atmosphere. For this purpose, we present theoretical absorption spectra of Na and Ca+ broadened by He for the conditions prevailing in cool white dwarfs.
- Published
- 2014
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